1. Field of the Invention
The present invention relates to an amorphous polymer and a process for production thereof, and a catalyst for polymerizing an olefin. More specifically, the present invention relates to an amorphous polymer having a high molecular weight enough to improve problems such as stickiness, elution to an organic solvent and the like, and to exhibit an elastomeric property and substantially not having a melting point, an olefin polymerization catalyst suitable for producing said amorphous polymer and a process for producing said amorphous polymer.
2. Description of Related Arts
An amorphous poly(.alpha.-olefin)(for example, an atactic polypropylene and an atactic poly(1-butene)) has been mainly used as a sticking agent, an improving agent for a crystalline polyolefin and the like. However, the molecular weight of an amorphous poly(.alpha.-olefin), as known well, is not high enough, therefore the amorphous poly(.alpha.-olefin) has problems such as stickiness of a product, elution to an organic solvent and the like, and it is difficult to say that an elastomeric property is sufficiently exhibited.
With respect to a synthesis of the amorphous polymer, Some processes have been known. It has been known from old times that a low-crystalline polymer prepared as a by-product is recovered when an olefin is polymerized with a solid Ziegler-Natta catalyst and an isotactic polymer is produced. However, the polymer obtained then has a low molecular weight and wide molecular weight distribution, and there have been problems such as stickiness of a product, elution to an organic solvent and the like.
Further, there are a report (Chem. Commun., 1996, 783) in which a high molecular weight poly(1-hexene) can be synthesized by polymerizing 1-hexene under a ultra-high pressure of 250 Mpa with a catalyst composed of using a hafnocene dichloride compound and methyl aluminoxane, and a report (EP0604917 A2 and EP0604908 A2) in which a polypropylene having a weight average molecular weight Mw of 377,000, a molecular weight distribution Mw/Mn(number average molecular weight) of 2.64 and a viscosity [.eta.] of 2.28 dl/g, and a poly(1-butene) having a viscosity [.eta.] of 1.29 dl/g, can be synthesized by polymerizing propylene with a catalyst composed of dimethylsilylene bis(9-fluorenyl) zirconium dichloride and methyl alumoxane, but a polymer having an adequate high molecular weight and narrow molecular weight distribution is not obtained.
On the other hand, a polymer having a Mw of more than 8.times.10.sup.6 can be synthesized (Macromolecular Chemie, Rapid Communication, Vol.10 (1989), page 349) by polymerizing propylene using a transition metal compound having an aryloxy ligand as a catalyst component, but the glass transition temperature of the polymer was somewhat high and an elastomeric property was not sufficient. Further, in the polymerization of an olefin having 4 or more carbon atoms with such catalyst, the resulted polymer was also not always satisfactory in the points of stickiness and elution property to an organic solvent.
As described above, a poly(.alpha.-olefin of 4 or more carbon atoms) which has an adequate high molecular weight and narrow molecular weight distribution and no melting point substantially, and is amorphous, is not obtained.